Electrodeposition of selenium from 1-ethyl-3-methyl-imidazolium trifluromethylsulfonate

The electrodeposition of thin selenium (Se) films from 1-ethyl-3-methyl-imidazolium trifluromethylsulfonate at room and elevated temperatures on gold and on copper substrates was studied under open-air conditions. The effect of bath temperature on the composition and structure of the deposited films was examined using cyclic voltammetry, chemical analysis and X-ray diffraction analysis. The obtained results showed that on gold substrate and at room temperature, a reddish Se film grows mainly in amorphous, monoclinic, rhombohedral and hexagonal structure, while at temperatures ≥90 °C, a grayish film of hexagonal and rhombohedral structure is deposited. Photoelectron spectroscopy shows that both films consist of pure Se with only slight surface contaminations by remnants from the electrodeposition. Due to the differences in phase structure and the presence of the monoclinic phase, the reddish films showed higher light absorbance. The band gap of the reddish film is close to that of pure amorphous Se reported in literature. Deposition on copper substrate leads to formation of CuSe and CuSe₂ at room temperature and at 70 °C, respectively.